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July 22; 1930. H. WEICHSEL .Re. 17,742

ALTERNATING CURRENT MOTOfi Original Filed Nov; 12, 1925 INVEN'TOR ATTORNEY named July 22. 1930 UNITED STATES PATENT OFFICE.

ms WEICHSEL, or

- My invention relates to an alternating'current motor capable of operating both as an induction and as a synchronous motor. Figtwo-pole polyphas'e motorembodying the invention, and Figure 2 moreclearly represents the windings on therevolving member. My invention is applicable to single as Well as to polyphase motors, but I will first describe it as applied to a poly phase machine.

I prefer to make use of a structure without defined polar projectionson either member as .is customary for single and polyphase induction motors, and while the primary member may be either stationary or revolving, I will describe my improvements as applied to a motor With a revolving primary. This revolving primary carries a commuted winding 2 combined and interconnected with a star connected polyphasewinding, 3, 4, 5, the commutedwinding 2 being located in the center or zero point of the star. This commuted winding can be looked upon as a delta connected three-phase winding located at the middle point of the star connected three-phase winding 3, 4, 5. Slip-rings 12, 13, 14 are attached to one end of each of the three phases of the star connected polyphase rotor winding and provide the means for connecting the machine to the supply. Brushes 6, 7 cooperate commutator such as is usually used in connection with such windings, and these brushes are connected to a Windin 8 located on the stator, the axis of-this winding being dislaced from the brush axis by a small-angle. ane value of this angle which I-havefound to give good results lies in the neighborhood of electrical degrees. A regulating resistance 11 is included in the circuit of this windin 8. The stator further carries a winding 9 displaced by 90 electrical degrees from the winding 8 and adapted to be closed over an adjustable resistance 10, all of which can, when desired, be cut out of circuit Referring to the operation of the motor shown in Figure 1, at starting a certain amount of resistance'is included in the circuit of each of the stator-windings8 and 9, the former being left connected to the brushes TION, OF ST. LOUIS, MISSOURI, A CORPORATION OF ure 1 is a diagrammatic representation of a with the commuted winding 2 by means of a DELAWARE ALTERNATING-CUBRENT MOTOR Original No. 1,558,845, dated September 15, 1925, Serial No. 874,131, filed November 12, 1923. Application for reissue filed Oetober lfl, 1926. Serial No. 142,414.

s'r. LOUIS, mrssoom, ASSIGNOR 'ro WAGNER Emo'rmc conronA.

6, 7 and the slip-rings are connected to the V supply. The two stator windings now do duty as polyphase secondary or induced windings and the machine starts with good torque and relatively small current. As the speed increases, the resistance in circuitwith each of the two stator windings can be reduced in one or more steps until the Winding 9 is shortcircuited andthe resistance of the circuit containing the winding 8 has been brought back to its operating value. As thespeed increases,

the induction motortorque of the machine decreases and becomes very small indeed, near synchronism, andis incapable of bringing the machine into synchronism. It is, however, desirable to cause the machine to run synchronously in normal operation for the reason that the power factor of such a motor can be readily adjusted if provision is made for producing a unidirectional excitation through the machine. In this case theunidirectional excitation is derived from the commuted winding 2, which, at synchronism, acts like a converter winding in a manner now Well understood. The direct current derived from the Winding 2 at synchronous speed is conducted through the stator winding 8 and the latter produces the desired unidirectional magnetization. But this winding 8 being so 7 connected to the rotor that the E. F. in-

eration, one component of which is so 10 cated as to satisfactorily influence the power factor. I have found that angles from 10 to electrical degrees give good results.

Should the machine at any time become overloaded when operating as a synchronous motor and fall out of step, it will continue to operate with good torque as an induction A motor, the two stator windings 8 and 9 again doing duty as polyphase secondary or induced windings In order to secure the best utilization of the winding space on the rotor, and at the same time secure such a low voltage on the commutator as will permit of a sufiiciently small number of turns per commutatorbar to insure perfect commutation, I have combined the commuted winding 2 with the three-phase star winding 3, 4, 5, placing theformer in the middle of the star. It will be understood that this commuted winding acts like the armature winding of. an ordinary rotary converter and in order to take the fullest advantage of this condition,-I prefer whenever possible, to so select the constants of my machine. as to make-the unidirectional exciting current sent into the winding 8 under synchronous operation about equal to the alternating current sent into the rotor. :Un-

remember that the-armature reaction in the single-phase machine has one unidirectional component and another component of double frequency. The short-circuited winding 9 on the stator can damp out or eliminate this double frequency component, and themachine may be started in any well known manner applicable to the starting of singlephase motors.

If, in themachine herein described, the brush axis is made to coincide with the axis of the Winding S the E. M. E. impressed on the winding 8 will be 00- hasal with'the E.IM. F, induced therein y the primary winding, and the torque,-the resultant of the induction motor torque and the pulsating torque due to the impressed E. M. F.has the highest possible value. The torque existing just prior' to synchronism and which is' hereinbefore referred to as synchronizing torque, is almost entirely due to the impressed M. F. since at this time the induced E. M. F. has become almost zero.

Displacing the brushes from the coaxial position decreases the value of the accelerating torque for the reason that the E. M. F. induced and the E. .M. F. impressed on the winding 8 are no longer co-phasal and decreases the value of the synchronizing torque since it. will then have negative components,

but the torque" curve is such that displacement of the brushes 20 degrees, for example, from the exciting winding does not as greatly diminish either the accelerating-or syn-V degree position to a 40 degree position. 4

When the brushes are coaxial with the exciting winding 8 the synchronizing torque is unidirectional in that it has no negative component, and by therexpression.substantially unidirectional synchronizing torqueused in the claims, I intend to include not chronizing torque as would a shift from a 20 only exactly unidirectional synchronizing torque but torques in which .the negative maxima are less than 18% of the'positive maxima, or in other words, when the angle 1 between the brush axis and the axis of the exciting winding 8 is less than degrees.

Also the E. M. F. induced in the exciting winding 8 and the E. M. F. im ressed thereon are to be deemed to be of a cut the same phase, when the brushes are coaxial with the exciting winding or displaced therefrom by an angle less than 45 electrical degrees. The

magnitude of the effective auxiliary voltage impressed on the winding 8 from the brushes,

remains substantially constant during the accelerating and synchronizing period and is of slip frequency.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is;

1. In a synchronous-induction motor, the combination of an inducing member provided with a commutator and brushes thereon,

,means for supplying alternating current to the inducing member, and an induced memher having an exciting winding displacedbv a small angle from the axis of said brushes, said angle being less than 45 electrical degrees.

2. In a synchronous-induction motor, the

combination of an inducing member provided with a commutator and brushes thereon, means for supplying alternating current i to the inducing member, an induced member havlng an exciting winding in circuit with the brushes and displaced by a small angle from the axis of said brushes, said angle being lessthan'45 electrical degrees, and a second winding on the induced member and displaced from the exciting winding.

3. In a synchronous-induction motor, the I combination of an inducing member pro.-

vided with a commutator and brushes thereon, means for supplying alternating current to the inducing member, an induced member 1 havmg an exciting wlndmg n circuit with the. brushes and displaced by a small angle from the axisof said brushes, said angle being less than 45 electrical degrees, and a second wmdmg on the induced member closed -on itself and displaced from the exciting s winding.

4. In a synchronous-induction motor, the combination of aninducing member provided with a commutator andbrushes thereon, means for supplying alternating current to the inducing member, an induced member having an exciting winding in circuit with the brushes and displaced y a small angle from the axis of said brushes, said angle be ing less than electrical degrees, a resistance in circuit with-\said exciting winding,

'and means forcutting out said resistance after the motor is started. a

'5. In a synchronous-induction motor, the combination of an inducing member provided with a commutator and brushes thereon, means for supplying alternating current to the inducing member, an induced member having an exciting winding in circuit with the brushes and displaced by a small angle from the axis of said brushes, said angle being less than 45 electrical degrees, a second winding on the induced member closed on itself and displaced from the exciting winding, a resistance in circuit with the exciting winding, and means for cutting out said resistance after the motor is started.

' 6. In a synchronous-induction motor, the combination of a rotor provided with a commutator and slip-rings, brushes on the commutator, a stator having an exciting Winding displaced by a small angle from the axis of the brushes and in circuit therewith, said angle being less than 45 electrical degrees, a second winding on the stator closed on itself and displaced from the exciting winding, resistances in circuit with each of said stator windings, and means for cutting out said resistances after the motor is started.

7. In a synchronous-induction motor, the combination of a rotor provided with a commuted winding and apolyphase winding, said windings being interconnected, a commutator and slip-rings connected to the commuted and polyphase windings respectively, brushes on the commutator, a stator having an exciting winding in circuit with said brushes and displaced therefrom by an angle less than 45 electrical degrees, a second winding on the stator displaced from the exciting winding, resistances in circuit with each of said stator Windings, and means for cutting out said resistances after the motor is started.

8. In a synchronous-induction motor, the

a combination of an inducing member provided with a commutator and brushes thereon, means for supplying alternating current vto the inducing member, and'an induced member having an exciting winding in circuit with the brushes and displaced by more than 45 electrical degrees from that axis of the machine which is at right angles to the brush axis.

9. The method-of operating a motor which carriesvvariable load at synchronous speed, comprising, producing a primary flux which revolves With respect to the primary, causing the primary flux to generate starting-torqueproducing ampere turns in a circuit on the secondar producing an auxiliary voltage of slip equency which becomes unidirectional and difl'ers from zero at synchronism, and impressing the auxiliary voltage on the starting-torque-producing circuit on the secondary to produce a substantially unidirectional synchronizing torque.

10. The method of operating ,a motor which carries variable load at synchronous speed, comprising, producing between the stator and rotor near synchronism a substantially unidirectional torque and causing this torque to lock the motor in synchronism.

11. The method of operating a motor which carries variable load at synchronous speed, comprising, producing between the stator and rotor near synchronism a substantially unidirectional synchronizing torque causing the torque increase as synchronism is approached and maintaining the.

torque until synchronism is reached.

12. The method of operating a motor which carries variable load at synchronous synchronizing speed, comprising, starting the motor by pro;

ducing between the stator and the rotor an induction motor torque which decreases as synchronism is approached and synchronizing the motor by producing a'substantially unidirectional torque which increases until synchronism. is reached.

13. A motor which carries variable load at synchronous speed, having a primary member carrying a Winding adapted to produce a primary flux which revolves with respect to the primary, a secondary member and a circuit thereon in inductive relation to the primary flux, a, source of auxiliary voltage of slipfrequency which becomes unidirectional and dif- :ters from zero at synchronism, and means adapted to produce near -synchronism and in cooperation with said primary flux a substan-' tially unidirectional synchronizing torque which is maintained until synchronism is reached, said means including the circuit on the secondary and said source for setting up at sub-synchronous speeds secondary ampere turns of about the same phase as the ampere turns generated in said secondary circuit by the primary flux.

14:. A motor which carries variable load at synchronous speed, having a primary member carrying a winding adapted to produce a primary flux which revolves with respect tothe primary, a secondary member and circuits thereon adapted to magnetize the secondary along displaced axesand to start the machine as an-induction motor, a source of auxiliary voltage of slip frequency which becomes unidirectional and differs from zero at synchronism, and means adapted to produce near synchronism and-in cooperation with I.

said primary fiux a substantially unidirectional synchronizing torque which is maintained until synchronism is reached, said means including one of the circuits on the secondary and said source forsetting up at subsynchronous speeds auxiliary secondary am-' pereturns of about the same phase as the ampereturns generated in the same secondary circuit by the primary flux.

5 15. The method of operating a motor which carries variable load at synchronous speed,

' com rising, roducing a primary flux which revo ves wit respect to the primary, causing the primary flux to generate induction-mom tor-torque producingampereturnson the sec- 'ondar introducing into a winding on the secon ary'an auxillary voltage of same fre quency and of about the same phase as the voltage generated in the secondary winding by the primary flux at ne'arlysynchronous s eeds, and maintaining the magnitude of ,t e auxiliary voltage until synchronism is reached to produce a synchronizing torque.

16 A motorwhich carries variable load at n synchronous speed, comprising, a primary member having a winding adapted to produce a primary flux which revolves with respect to the rimary, a secondar member having a win ing, means for pro ucing and impressing on the secondary winding :1 synchronizing voltage of a magnitude independent of its frequency and of same frequency as that of the voltage generated in said winding by the primary flux, and means for controlling the 80 phase of the synchronizing voltage adapted, at speeds very near the synchronous, to cause it to pass through'zero approximately when the axis of the secondary winding coincides with the axis of the rimary flux. 1

I 17. 'A motor whic carries variable load at synchronous speed, having a primary member adapted to produce a primary flux which revolves with respect to the primary, a secondary member having a winding in inductive re- 40- lation to the primary flux,'asource of auxiliary voltage, and means including the winding on the secondary and said source adapted to produce a substantially unidirectional and pu sating synchronizing torque between primary and seconda members, whereby the 7 motor can be broug t into synchronism and caused to operate synchronously at a plurality of loads. 18. A synchronous motor adapted'for oporation as an induction moto'r at sub-synchronous'speeds and comprising an inducing member provided with a commutator and slip rings, brushes on the commutator, an induced memberhaving an excitin winding displaced by a small angle from t 0 axis of g the brushes and in circuit therewith, said angle being not greater, than approximately 30 electrical degrees and not less than approximately 10 e ectrical degrees, and a second -6 winding on the induced member, said windingbeing closed on itself and displaced from the exciting winding, y

In testimony whereof, I hereunto aflix my signature,fthis'15th day of October, 1926.

' HAN S WEIOP- 

